Separation of higher boiling impurities from liquefied gases

Abstract

For separating a higher boiling component from a liquefied gas, e.g., CO, rectification is used wherein a partial stream of the liquefied gas is vaporized, superheated, and then fed into the lower portion of a rectification column. The remainder of the liquefied gas in the liquid phase is fed into the upper portion of the rectification column. The rectification results in the higher boiling component being concentrated in the bottoms, and the overhead gas product being purified thereby. Additional purification is possible by liquefying and refluxing part of the overhead gas product, and in this case, it is possible to superheat the entire liquefied gas so as to obtain ultra high purity product.

What is claimed: 
     
       1. A process for a low temperature separation of a higher boiling component from a liquefied gas by rectification, comprising vaporizing a partial stream of the liquefied gas, providing a heat exchanger specifically designed to enable replacement of the sump heater or reboiler of the column by super-heating the resultant vapor in said heat exchanger and introducing the resultant superheated vapor into the lower portion of a rectification column, passing the remainder of the liquefied gas in the liquid phase into the upper portion of the rectification column, and conducting rectification so as to withdraw said higher boiling component as bottoms and to recover vaporized liquefied gas depleted in said higher boiling component, as overhead gas product. 
     
     
       2. A process according to claim 1, further comprising vaporizing and super-heating the liquefied gas in indirect heat exchanger relationship with gas to be liquefied. 
     
     
       3. A process according to claim 2 further comprising heating, compressing and liquefying a partial stream of said overhead product gas and returning via a pressure reduction zone resultant liquefied partial stream of gas overhead as reflux into the upper portion of the rectification column. 
     
     
       4. A process according to claim 3, said reflux being introduced into the rectification column above the feed point of the liquid phase liquefied gas. 
     
     
       5. A process according to claim 4 wherein the liquefied gas is CO and the higher boiling component comprises methane. 
     
     
       6. A process according to claim 3 further comprising liquefying said compressed partial stream of overhead product in indirect heat exchange relationship with the overhead product gas to be heated and with the bottoms product. 
     
     
       7. A process according to claim 6 wherein the liquefied gas is CO and the higher boiling component comprises methane. 
     
     
       8. A process according to claim 3 wherein the liquefied gas is CO and the higher boiling component comprises methane. 
     
     
       9. A process according to claim 2 wherein the liquefied gas is CO and the higher boiling component comprises methane. 
     
     
       10. A process according to claim 9 wherein the higher boiling component amounts to less than about one volume percent. 
     
     
       11. A process according to claim 1 further comprising heating, compressing and liquefying a partial stream of said overhead product gas and returning via a pressure reduction zone resultant liquefied partial stream of gas overhead as reflux into the upper portion of the rectification column. 
     
     
       12. A process according to claim 11, said reflux being introduced into the rectification column above the feed point of the liquid phase liquefied gas. 
     
     
       13. A process according to claim 12 wherein the liquefied gas is CO and the higher boiling component comprises methane. 
     
     
       14. A process according to claim 11 further comprising liquefying said compressed partial stream of overhead product in indirect heat exchange relationship with the overhead product gas to be heated and with the bottoms product. 
     
     
       15. A process according to claim 14 wherein the liquefied gas is CO and the higher boiling component comprises methane. 
     
     
       16. A process according to claim 11 wherein the liquefied gas is CO and the higher boiling component comprises methane. 
     
     
       17. A process according to claim 16 wherein the higher boiling component amounts to less than about one volume percent. 
     
     
       18. A process according to claim 1 wherein the liquefied gas is CO and the higher boiling component comprises methane. 
     
     
       19. A process according to claim 18 wherein the higher boiling component amounts to less than about one volume percent. 
     
     
       20. A process as claimed in claim 1, wherein the higher boiling component to be separated comprises less than 5 mol % of the liquified gas. 
     
     
       21. A process as claimed in claim 1, wherein liquified gas refers to a gas having a boiling point below 400° K. at atmospheric pressure. 
     
     
       22. A process for a low temperature separation of a higher boiling component from a liquefied gas by rectification, comprising completely vaporizing the liquefied gas, providing a heat exchanger specifically designed to enable replacement of the sump heater or reboiler of the column by super-heating the resultant vapor in said heat exchanger and introducing the resultant superheated vapor into the lower portion of a rectification column, conducting rectification so as to withdraw said higher boiling component as bottoms and to recover vaporized liquefied gas depleted in said higher boiling component, as overhead gas product, compressing and liquefying a partial stream of said overhead product gas and returning via a pressure reduction zone resultant liquefied partial stream of gas overhead as reflux into the upper portion of the rectification column.